Hangfire indicator for automatic firearms



Jan. 18, 19% E. M. HARVEY 3,229,399

HANGFIRE INDICATOR FOR AUTOMATIC FIREARMS Filed Oct. 26, 1964 F'I ZL INVENTOR ATTORNEYS United States Patent 3,229,399 HANGFIRE INDICATOR FOR AUTOMATIC FIREARMS Earle M. Harvey, Agawam, Mass., assign'or to the United States of America as represented by the Secretary of the Army Filed Oct. 26, 1964, Ser. No. 406,624 1 Claim. (Cl. 42--1) (Granted under Title 35, US. Code (1952), see. 266) The invention described herein may be manufactured and used by or for the Government for governmental purposes without the paymentto me of any royalty thereon.

This invention relates to automatic firearms and pertains more particularly to safe devices therefor.

Whenever the firing of an automatic weapon using cartridge ammunition is interrupted before release of the trigger, problems are raised as to how the weapon may be safely handled. Three of the common causes for firing interruptions are: an empty barrel chamber caused by faulty feeding; failure of the firing pin to detonate the primer of the chambered cartridge, probably caused by firing mechanism trouble or poor ammunition; and failure of the primer at detonation to ignite the propellant.

With the first two of these causes, attempts may be immediately initiated for resuming firing by charging the weapon which will eject any faulty cartridge and feed a fresh one into the barrel chamber. However, the third cause may be the result of a hangfire condition and, therefore, if the Weapon should be recharged, serious bodily harm and material damage may result if the cartridge should explode after the breech is opened or while the cartridge is being ejected.

Some automatic pistols are provided with means for indicating whether they are loaded and cocked but until now there has not been any way to quickly ascertain in a machine gun whether a cartridge is in the barrel chamher after firing is interrupted and, if there is, whether or not the primer has been detonated. Therefore, it has to be presumed for safety reasons that a hangfire condition does exist, whereby a prescribed waiting period of 30-60 seconds must be observed. In battle this delay, or a gambling disregard of the safe waiting period, could be costly. In tests, too, considerable valuable time is wasted because of the many firing interruptions which are inherent in the testing operations during development of a gun.

It is, therefore, the principal object of this invention to provide a means for quickly and positively indicating, when firing is interrupted, whether a cartridge is chambered in the barrel and if so Whether its primer has been detonated.

The specific nature of the invention as well as other objects and advantages thereof will clearly appear from a description of a preferred embodiment as shown in the accompanying drawings in which:

FIG. 1 is a fragmentary, longitudinal view of a firearm showing the bolt in battery position and the barrel chamber empty;

FIG. 2 is an enlarged, fragmentary view similar to FIG. 1 but showing a cartridge in the chamber; and

FIG. 3 is a view similar to FIG. 2 but showing the primer of the chambered cartridge detonated.

Shown in the figures is a machine gun 12 having a receiver 14 with an open top which is closed by a pivotal cover 15 and a barrel 16 with a chamber 18 for receiving a cartridge 20. Cartridge 20 is provided with a propellant 22 and a primer 24 having a primer cup 26. A bolt 28 is mounted in receiver 14 for reciprocation between a battery position wherein cartridge 20 is blocked "ice in chamber 18 and a recoil position and such bolt carries a firing pin 30 which is actuatable relative to the bolt to a striking position for detonation of primer 24.

Firing pin 30 includes a body portion 32 and a striker portion 34 of smaller diameter extending coaxially forward therefrom and the firing pin is accommodated in a stepped bore 36. Such stepped bore 36 includes a section 38 which slidingly receives body portion 32 and a reduced diameter section 40 which receives the striker portion 34. Reduced diameter section 40 is counterbored from the front end of bolt 28, as noted at 42, and is countersunk to form a conical bottom 44 to receive a piston 46 having a head 48 with a conical end 49 which mates with bottom 44 and a shank 50 which extends coaxially forward from an annular shoulder 52 around the rear of such head. An aperture 53 extends axially through piston 40 for receiving striker portion 34. Shank 50 is slidingly received by a bushing 54 which is threadingly mounted in the front end of counterbore 42 so that piston 46 is slidingly supported for movement between a forward position wherein shoulder 52 is in contact with the rear end of bushing 54 and a rearward position wherein conical end 49 is in contact with bottom 44. When piston 46 is in its forward position, the front end of shank 50, noted at 56, extends forwardly from the front end of bolt 28 and, when the piston is in its rearward position, the front end is located within bushing 54. The diameter of shank 50 is slightly larger than that of primer cup 26 so that the primer cup is projectable within bushing 54 when primer 24 is detonated.

An orifice 58 extends downwardly from the top of bolt 28 to interrupt bottom 44 of counterbore 42 and provide communication therewith and such orifice slidingly accommodates an indicator pin 60. The bottom of indicator pin 60 is arranged to slidingly contact conical end 49 which cammingly transfers the translational displacement of the indicator or piston 46 to the other. Indicator pin 60 is provided with an inverted well 62 which accommodates a compressible coil spring 64 the bottom end of which is supported by a rod 66 through the indicator pin. The top end of spring 64 has contact with a shaft 68 which extends through indicator pin 60 with the extending ends being received by mating holes (not shown) in bolt 28, whereby the indicator pin is biased downwardly and piston 46 outwardly to its forward position. Shaft 68 is received by a pair of vertical slots 72 with closed ends in indicator pin 60 to permit limited vertical displacement thereof between an extended and a retracted position.

Piston 46 and indicator pin 60 are so related that, when the piston is in its forward position, the top end of the indicator pin, noted at 74, is located below the surface of bolt 28 so that, when front end 56 is flush with the surface of the bolt, the top end of the indicator pin is flush with the surface of the bolt, and so that, when. the piston is in its rearward position, such top end extends above the bolt surface.

Piston 46 is normally biased by indicator pin 60 to its forward position so that, when the bolt goes into battery and chamber 18 is empty, as shown in FIG. 1, this condition, which presumes faulty feeding, is indicated by top end 74 being located below the surface of the bolt. When a cartridge 20 is in chamber 18, as shown in FIG. 2, and primer 24 has not been detonated, which would presume trouble in the firing mechanism, piston 46 is displaced rearwardly by con-tact of front end 56 with primer cup 26 to where top end 74 is flush with the surface of bolt 28. When a cartridge 20 is in chamber 18 and primer 24 is detonated by firing pin 36, primer cup 26 is set back into bushing 54 by the detonating force to displace piston 46 to its rearward position and this condition, which might variations.

be due to a hangfire, is indicated by top end 74 being located above the surface of bolt 28 as shown in FIG. 3.

Therefore, through this invention, the cause of any interruption of weapon 12 due to firing trouble is easily ascertainable by lifting cover 15 so that the relationship of top end 74 to the surrounding surface of bolt 28 can be checked and, unless indicator pin 60 shows that primer 24 has been detonated, attempts to resume firing may be immediately initiated by recharging machine gun 12. Consequently, time, which may be critical, is saved.

Although a particular embodiment of the invention has been described in detail herein, it is evident that many variations may be devised within the spirit and scope thereof and the following claims are intended to include such I claim:

In an automatic gun for firing a cartridge having a primer, 9. primer cup of the primer displaceable by detonation thereof, a barrel having a chamber for receiving the cartridge, a bolt actuatable from a recoil to a battery position for blocking the cartridge in said chamber, a firing pin slidingly mounted in said bolt for striking said primer cup to detonate the primer when said bolt is in the battery position, a piston slidingly mounted in said bolt for contact with said primer cup when the cartridge is in said barrel chamber and for displacement by said primer cup when the primer is detonated, means cooperating with said piston for indicating when the cart-ridge is in said chamber and when the primer of the cartridge therein is detonated, said means including a pin slidingly mounted in said bolt, cam means on said piston contacting said pin for transferring movement of said piston thereto, means for limiting displacement of said pin to movement between an extended and a retracted position, a spring acting against said pin for displacement thereof to the retracted position, a front end of said piston contactable by said primer cup of the cartridge when in said chamber to displace said piston from the forward position and to displace said piston further to the rearward position when said primer cup is displaced by detonation of the primer, a stepped bore in said bolt for receiving said firing pin, a counterbore of said bore extending into said bolt from the front end thereof for slidingly receiving said piston, an aperture extending through said piston for receiving a striker portion of said firing pin, a bushing mounted in the front end of said counterbore for slidingly supporting said piston and for receiving said primer cup when displaced by detonation of the primer to actuate said piston to the rearward position, a top end of said pin, an orifice extending from" the outside of said bolt into communication with said stepped bore, and said pin and said piston being so related that when said piston is in the forward position said pin is in the retracted position and said top end thereof is located below the surface of said bolt, when said front end is flush with the front end of said bolt said top end is flush with the surface of said bolt and when said front end is located Within said bushing said pin is in the extended position and said top end extends above the surface of said bolt.

References Cited by the Examiner UNITED STATES PATENTS 654,280 7/1900 Richards 421 802,279 10/ 1905 Fr-ommer 42-l 1,459,284 6/1923 Declaye 421 BENJAMIN A. BORCHELT, Primary Examiner.

R. V. LOTTMANN, Assistant Examiner. 

